U.S. patent application number 09/803864 was filed with the patent office on 2002-09-12 for floating drive for vehicle.
Invention is credited to Coveyou, Jon L..
Application Number | 20020124764 09/803864 |
Document ID | / |
Family ID | 25187641 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020124764 |
Kind Code |
A1 |
Coveyou, Jon L. |
September 12, 2002 |
Floating drive for vehicle
Abstract
A vehicle including a load frame, a drive assembly, and a pivot
link assembly. The load frame includes castor wheels to rollingly
support the load frame on a support surface. The drive assembly
includes a drive frame, a drive wheel, and a rigid castor wheel
wherein the drive wheel and rigid castor wheel are each mounted to
the drive frame. The pivot link assembly couples the drive frame to
the load frame and permits the drive frame to move vertically and
angularly relative to the load frame.
Inventors: |
Coveyou, Jon L.; (Petoskey,
MI) |
Correspondence
Address: |
Douglas A. Mullen
Dickinson Wright PLLC
Suite 800
1901 L. Street N.W.
Washington
DC
20036
US
|
Family ID: |
25187641 |
Appl. No.: |
09/803864 |
Filed: |
March 12, 2001 |
Current U.S.
Class: |
104/137 ;
180/6.2 |
Current CPC
Class: |
B62D 53/005 20130101;
B62D 61/12 20130101 |
Class at
Publication: |
104/137 ;
180/6.2 |
International
Class: |
B61B 013/00 |
Claims
What is claimed is:
1. A vehicle comprising: a load frame having castor wheels to
rollingly support the load frame on a support surface; a drive
assembly including a drive frame, a drive wheel, and a rigid castor
wheel, said drive wheel and rigid castor wheel mounted to said
drive frame; and a pivot link assembly coupling the drive frame to
the load frame and permitting the drive frame to move vertically
and angularly relative to said load frame.
2. The vehicle of claim 1 wherein said pivot link assembly includes
a pair of pivot rails each having a first end pivotally coupled to
the load frame and a second end pivotally coupled to the drive
frame.
3. The vehicle of claim 2 wherein the pivot link assembly further
includes a plate extending between the pivot rails, said plate
being positioned below the drive frame and including a cutout, said
rigid castor wheel positioned for vertical movement within said
cutout.
4. The vehicle of claim 1 wherein said drive assembly includes a
second rigid castor wheel mounted to said drive frame, said drive
wheel and said rigid castor wheels being positioned to form a
triangle.
5. The vehicle of claim 4 wherein the first end of the pivot link
assembly is coupled to the drive frame at a bearing block, wherein
the triangle is oriented so that the point defined by the drive
wheel positioned forward of the bearing block.
6. The vehicle of claim 1 wherein said drive wheel is rotatable
about a first axis to drive said cart and rotatable about a second
axis to steer said cart.
7. The vehicle of claim 1 wherein said pivot link assembly couples
said drive frame to said load frame to permit said drive frame to
rotate relative to said load frame.
8. The vehicle of claim 1 wherein said drive assembly further
includes a power source and a controller on board said drive frame,
said controller communicatingly coupled to said drive wheel so that
said drive assembly is operable as an autonomous vehicle.
9. The vehicle of claim 1 further including a biasing mechanism to
urge the drive frame downward relative to the load frame.
10. The vehicle of claim 9 wherein said spring is a coil
spring.
11. The vehicle of claim 1 further including a stop assembly fixed
to the load frame to limit vertical movement of the drive frame
relative to the load frame.
12. The vehicle of claim 11 wherein said pivot link assembly
further includes a second stop assembly for limiting rotation of
the drive frame relative to the load frame.
13. A vehicle comprising: a load frame having load wheels; a drive
wheel; a rigid castor wheel; and a pivot link assembly coupling the
drive wheel and the rigid castor wheel to the load frame to permit
said drive wheel and rigid castor wheel to move vertically relative
to said load frame.
14. The vehicle of claim 13 further including a drive frame,
wherein said drive wheel and said rigid castor wheel are mounted to
said drive frame, and wherein said pivot link assembly couples said
drive frame to said load frame and permits the drive frame to move
vertically relative to said load frame.
15. The vehicle of claim 14 wherein said pivot link assembly
couples said drive frame to said load frame and permits the drive
frame to move vertically and rotate relative to said load frame.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is generally directed to material
handling vehicles and, more particularly, to a vehicle having a
vertically floating drive assembly.
[0002] Automatic guided vehicles (AGVs) are used throughout the
material handling industry to transport loads. The term AGV is
commonly used to refer to robust vehicle designs having any of a
number of available automated guidance systems. Automatic guided
carts (AGCs) is a term commonly used to refer to a less robust
vehicle used for similar but smaller-scale applications. Current
AGC designs generally include a frame with swivel castors located
at the four corners of the frame. Other features may include a
drive wheel assembly and rigid castors for directional control of
the cart. In one current design, two rigid castors are fixed to the
frame and located approximately midway between the swivel castors
on each side of the cart frame. The two pair of swivel castor axes
and the rigid castor axis are generally parallel to each other. The
steerable driving unit is attached to the cart frame, generally by
way of a plate that is hinged and spring loaded from the cart frame
to ensure that the steerable drive wheel maintains adequate
traction with the support surface.
[0003] While this arrangement is generally acceptable for uniform
support surfaces, situations where the floor is not level and flat
may give rise to losses in the directional control of the cart.
More particularly, when the cart encounters an uneven surface, the
direct mounting of the swivel and rigid castors to the cart frame
may cause one or more of the three sets of castors to become
disengaged from the support surface. Since the rigid castors are
used for direction control of the cart, loss of contact between the
rigid castors and the floor may cause loss of directional control
of the cart. The only wheel that has significantly uniform contact
with the floor is the hinged and spring loaded steerable drive
wheel.
SUMMARY OF THE INVENTION
[0004] In view of the above, a need exists for a AGC design that
more effectively maintains directional control for the cart or AGV.
More particularly, a need exists to maintain both the steerable
drive wheel and at least one rigid castor in contact with the floor
surface at all times.
[0005] To meet these and other needs that will be apparent to those
skilled in the art based upon this description and the appended
drawings, the present invention is directed to a material handling
vehicle having a load bearing support frame with wheels to
rollingly engage a support surface as well as a drive assembly
having a drive frame supporting a drive wheel and a rigid castor. A
pivot link assembly rotationally coupled to the load frame and the
drive frame permits the drive frame to vertically float and change
angular orientation relative to the drive frame thereby ensuring
that the drive wheel and rigid castor maintain operative contact
with the support surface even on uneven contours.
[0006] Further scope of applicability of the present invention will
become apparent from the following detailed description, claims,
and drawings. However, it should be understood that the detailed
description and specific examples, while indicating preferred
embodiments of the invention, are given by way of illustration
only, since various changes and modifications within the spirit and
scope of the invention will become apparent to those skilled in the
art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention will become more fully understood from
the detailed description given here below, the appended claims, and
the accompanying drawings in which:
[0008] FIG. 1 is an underside perspective view of an AGC according
to the present invention;
[0009] FIG. 2 is an upper perspective view of the drive assembly
and float coupling assembly illustrated in FIG. 1;
[0010] FIG. 3 is a perspective view of the drive assembly;
[0011] FIG. 4 is a perspective view of the pivot link assembly;
[0012] FIG. 5 is a side perspective view of the AGC shown in FIG. 1
with a side load frame tube removed for clarity;
[0013] FIG. 6 is a side elevational view of the cart shown in FIG.
5 with the drive assembly in its centered position;
[0014] FIG. 7 is a side elevational view of the cart shown in FIG.
5 with the drive assembly in its fall up position and rotated
counterclockwise;
[0015] FIG. 8 is a side elevational view of the cart shown in FIG.
5 with the drive assembly in its fall down position and rotated
clockwise; and
[0016] FIG. 9 is a sectional view take along the line 9-9 shown in
FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] An automated guided cart 10 according to the present
invention is illustrated and described with reference to FIGS. 1-5.
It should be appreciated that the applications for the vertically
floating drive unit according to the present invention may be used
in a variety of applications beyond the illustrated AGC. For
example, the present invention may be used with automated guided
vehicles of a variety of configurations as well as other material
handling vehicles permitting the vehicles to function with greater
precision along unevenly contoured surfaces.
[0018] The AGC 10 includes a load frame 12 supported at each of its
corners by swivel castors 14. A drive assembly 16 includes a drive
frame 18, a drive wheel 20, and a pair of rigid castors 22. The
drive wheel 20 and rigid castors 22 are each fixed for movement
with the drive frame 18. As is conventionally known, the drive
wheel 20 is rotatable about a drive axis 24 and a steering axis 26.
Each of the rigid castors 22 are rotatable only about a single axis
28 oriented perpendicular to the AGC's longitudinal axis 30.
Accordingly, when the rigid castors are engaged with the cart
support surface, the castors tend to maintain the directional
control of the cart in its axial direction.
[0019] A pivot link assembly 36 interconnects the drive assembly 16
with the load frame 12 through two pivot axes thereby permitting
the drive assembly to vertically float relative to the load frame.
The pivot link assembly 36 also is configured to permit the angular
orientation of the drive assembly 16 to vary within a predetermined
range relative to the load frame 12. These vertical and angular
degrees of freedom maintain the drive wheel unit 20 and rigid
castors 22 in contact with the cart support surface, even when the
support surface has an uneven contour.
[0020] In the illustrated embodiment, the pivot link assembly 36
includes first and second side rails 38 and 40 (FIG. 4)
interconnected by a support plate 42. The rails are pivotally
coupled at each of their respective ends to the load frame 12 via
frame bearing blocks 44 and to the drive frame 18 via drive unit
bearing blocks 46. A first pivot shaft 50 rotatably connects the
rearward end of the rails 38 and 40 and support plate 42 to the
frame bearing blocks 44. In a similar manner, the forward ends of
the rails 38 and 40 are rotatably coupled to the respective drive
unit bearing blocks 46. The pivot shafts 50 and 52 are preferably
oriented parallel to one another and parallel to the rigid castor
axis 28.
[0021] While the pivot link assembly 36 may have a variety of
configurations, the illustrated embodiment includes cut-outs 56 in
the plate 42 to receive the rigid castors 22. The vertical float
and angular reorientation capability of the drive assembly, as well
as the tricycle configuration of the drive wheel and rigid castors,
maintain the steerable drive wheel and at least one rigid castor in
contact with floor surfaces having uneven contours. As a result,
the drive/directional control integrity of the AGC is superior to
previous cart designs. An illustration of the float and angular
reorientation capability of the present invention is provided in
FIGS. 6-8. Specifically, FIG. 6 is a side elevation view of the
cart 10 with the drive assembly 16 in its centered position, i.e.,
with the bearing surfaces of the drive wheel 20, rigid castors 22,
and swivel castors 14 at the same elevation. When the cart
encounters an uneven surface, the drive assembly 16 is pivotable
relative to the load frame 12 about axes 50 and 52 to provide
vertical float and angular reorientation. For example, the drive
assembly 16 is illustrated in FIG. 7 in its full up position and
rotated counterclockwise and in FIG. 8 in its full down position
and rotated clockwise. It should be appreciated that these
orientations are illustrated for exemplary purposes and that the
range of movement of the drive assembly is not necessarily limited
to the specific orientations or ranges illustrated and described
herein.
[0022] The range of vertical float and pivoting movement permitted
by the pivot link assembly 36 is preferably limited by
appropriately configured and positioned pivot stops. In the
illustrated embodiment, the range of vertical float is limited to
one inch, with one-half inch of float being provided above and
below the centered position shown in FIG. 6. Additionally, a
biasing mechanism is preferably operatively positioned between the
load frame and the drive frame to apply a downward spring loading
on the tricycle drive assembly 16. This additional loading enhances
the traction of the drive wheel 20 and rigid castors 22 with the
support surface. Finally, it is also desirable to include one or
more rotation stops to prevent over-rotation of the drive frame 18.
As most clearly illustrated in FIG. 2, the drive wheel 20, and its
associated limit switches and actuators 59, are generally
positioned at the forward end of the frame 18. A power source, such
as the illustrated pair of batteries 58, are in a center
compartment and a rear compartment accommodates the control
electronics for the cart. In this configuration, the loading on the
drive frame 18 tends to rotate the drive assembly in a
counterclockwise direction about axis 52 as indicated by arrow 54.
The rotation stops are used to limit this rotation.
[0023] One skilled in the art will appreciate that numerous pivot
and rotation stop configurations, such as brackets, bolts, and the
like, may be used to limit the vertical float and rotation of the
drive assembly and that a variety of springs or other biasing
mechanism may serve to maintain drive traction. For example, the
illustrated embodiment includes stop assemblies 60 that are
positioned proximate the drive unit bearing blocks 46 (FIGS. 5-9)
and that serve as the pivot stops and bias mechanism for the drive
assembly 16. Each stop assembly 60 includes a spring bracket 62
fixed to the load frame 12 and a coil spring 64 disposed about a
bolt 65. The spring 64 is compressed between the bracket 62 and
pivot plate 42 to exert a downward bias on the plate. A down stop
washer 66 is normally spaced a predetermined distance from the
bracket 62 by a spacer tube 68. Thus, the drive assembly 16 is able
to pivot downward from its centered position (FIG. 6) until the
washer is displaced the predetermined distance and abuts the
bracket 62 (FIG. 8). The upward pivot stop is provided by a stop
flange 70 (FIGS. 5 and 9) that is fixed to the drive frame 18 and
that includes a leg 72 positioned to abut the load frame 12 or
bracket 62 when the drive assembly 16 is in its full up position
(FIG. 7).
[0024] Finally, in the illustrated embodiment, a rotation stop
assembly 76 is positioned proximate the forward end of the drive
assembly 16. The rotation stop (FIG. 5) includes a rotation bracket
78 having a slot 80 within which a stop pin 82 is disposed for
movement. The bracket 78 and pin 82 are each fixed to one of the
drive frame 18 and load frame 12 so that relative frame movement is
limited by bracket/pin abutment. Notwithstanding the above
description of the stop assemblies 60, spring 64, and stop assembly
76, those skilled in the art will appreciate that a variety of
equivalent mechanisms known in the art may be used to provide the
stop and bias functions without departing from the scope of the
invention defined by the appended claims.
[0025] A further benefit of the use of the floating drive unit is
that the load frame 12 and drive frame 18 are independently loaded.
Thus, the payload supported by the load frame 12 and swivel castors
14 may be varied based upon operational goals whereas the loading
on the drive unit is dependent principally upon the weight of the
drive unit and any bias provided by the coil spring 62. Also, by
including on-board power, control, and mechanical components
necessary for autonomous movement, the drive assembly may be
disconnected from the load frame 12 and pivot link assembly 36 if
it is desired to use the drive assembly as an autonomous vehicle.
Possible applications for such autonomous use would include use as
a small towing device or lightweight cart where space constraints
prevented the effective movement of the larger load frame 12.
[0026] The foregoing discussion discloses and describes an
exemplary embodiment of the present invention. One skilled in the
art will readily recognize from such discussion, and from the
accompanying drawings and claims that various changes,
modifications and variations can be made therein without departing
from the true spirit and fair scope of the invention as defined by
the following claims.
* * * * *